Neuroscientists have long recognized the significance of using microelectrode arrays for recording extracellular potentials from populations of neurons, for which a number of such devices have been developed so far. However, current implantable microelectrode technologies to monitor single neuronal function in-vivo often fail in chronic situations, likely due to mechanical drift in positioning mechanisms, micromotion of brain tissue and gliosis around the implant site. The overall goal of the proposal is to develop a reliable technology for recording electrical potentials from single neurons in chronic experiments. We propose to develop a novel microfabricated thermal microactuator and associated microelectrode technology in collaboration with Sandia National Laboratories to enable repositioning of microelectrodes after implantation. The flexibility to reposition the microelectrodes after implantation (in the event of a failure or otherwise) using microactuators will potentially increase the reliability and consistency of single-neuronal recordings in-vivo in chronic experiments with awake and behaving animals. The key goals for developing this technology in this proposal are (a) to enable high quality, reliable single- unit electrical recordings from ensembles of neurons even in deep structures of the brain in awake, behaving rodents (b) to enable reliable positioning and repositioning of microelectrodes in both acute and long-term experiments and (c) assess the effect of microelectrode movement on the surrounding brain tissue. We will use a combination of modeling and simulation, novel microfabrication and packaging techniques, bench-top testing and in-vivo testing approaches for design, characterization and validation. Besides leading to novel discoveries in our own research into neuronal mechanisms of stroke injury and recovery, this new technology will immediately impact several NIH funded grants of our collaborators. The microactuated microelectrode will be tested in a scenario that demands accurate long-term recording from neurons in deep nuclei of the brain. Independent evaluation and dissemination will be ensured with the help of collaborators doing in vivo experiments for understanding the mechanisms of memory retrieval and consolidation and memory deficits in aging, auditory physiology, cortical prostheses etc. [unreadable] [unreadable]